The two victims have been identified as former longtime KOMO News photographer Bill Strothman and pilot Gary Pfitzner. Strothman worked for many years at KOMO News and was well-known to many of the employees.

The helicopter that crashed was not the regular KOMO helicopter but a temporary replacement for one that's in the shop for an upgrade.

Two cars and a pickup truck on Broad Street were struck by the helicopter when it crashed.

Occupants of two vehicles were able to escape without injury, but the driver of a third vehicle was badly burned. Witnesses said the 38-year-old Seattle man could be seen running from from his car with his clothing on fire, and he was extinguished by officers at the scene. The man suffered burns on his lower back and arm, covering up to 20 percent of his body, Harborview hospital spokeswoman Susan Gregg said. He was originally listed in critical condition but was upgraded to serious condition Tuesday afternoon, Gregg said.

The helicopter exploded into a fireball on impact. Huge flames and thick plumes of black smoke poured from the blazing wreckage, about 50 yards from the base of the Space Needle. Smoke poured over the city at the height of the morning commute.

Fuel gushing from the wreckage caught fire and burned for a block from the crash scene. Secondary explosions continued for several minutes afterward.

"Not only were the cars on fire, the fuel running down the street was on fire," said Seattle Fire Department spokesman Kyle Moore.

Firefighters stopped the burning fuel from entering the sewer.

Strothman was a longtime KOMO photojournalist.

"We all know him as one of the best storytellers to have ever graced the halls of KOMO," said news anchor and reporter Molly Shen. "It felt like a loss for us because he knows his craft so well, and he's such an artist and such a great journalist."

KOMO News anchor Dan Lewis said, "He really knew how his pictures could tell a million words. He put so much into getting just the right shots, the right video, putting it in the right place in the story."

He is survived by his wife Nora, a daughter, and his son Dan Strothman, who also is a KOMO News photojournalist.

The pilot, Gary Pfitzner, was also employed by the helicopter leasing company that operates Air 4 but was a familiar sight to KOMO News employees.

"He always had a smile on his face," Shen said. "He loved what he did, loved to be able to fly and be up there above the city and see things from a perspective that most of us don't get to see."

Witnesses said the helicopter crashed as it was taking off from the helipad on the roof of Fisher Plaza, across the street from the Space Needle, at about 7:40 a.m.

"It looked like the helicopter was trying to take off, and it just was trying to stabilize and it looked odd ... and it just took a nose dive right down there on the street," said one eyewitness. "And the scary thing about it was the gas from the helicopter started leaking and it caught a car or two on fire - so it's crazy."

Another eyewitness, Brian Cruz, said he saw the chopper in trouble in the air near the helipad.

"It looked like it got hung up on some cables, and before you know it - boom! - it dropped dropped to the street," he said.

Chris McOlgan was in a car just behind the crash.

"It just blew up instantly," McOlgan said. "Nothing could have been done."

Kristopher Reynolds, a contractor working nearby, saw the crash. He said the helicopter lifted about 5 feet and looked like it was about to clear the building when it tilted. It looked like it was trying to correct itself and then took a dive downward.

"Next thing I know, it went into a ball of flames," he said.

Fire crews were able to extinguish the flames within a half-hour. Traffic was diverted from the area.

An investigation is under way, and Broad Street will be closed overnight between Fourth and Fifth avenues as investigators continue their work. The Space Needle, Seattle Center Monorail and Experience Music Project museum were also closed Tuesday. Mayor Ed Murray said the crash site could be closed for three to five days while officials with the NTSB and Federal Aviation Administration probe what happened.

A woman from one of the burned cars went to a police station and talked to officers. The man from the pickup truck walked off. Fire investigators later located him and he was not hurt, officials said.

An hour after the crash, firefighters had put out the fires and were cleaning up the spilled fuel, which left a strong smell in the area.

Only the tail of the helicopter could be identified among the burned metal on the street next to the Seattle Center.

Workers here at KOMO rushed to the window when they heard the crash. Reporters with the station were then in the position of covering the deaths of colleagues.

"We mourn the loss of a couple of our co-workers today," KOMO-TV anchor Dan Lewis said on the air. "It's so difficult for us to look at this scene, of the wreckage down there."

On the street, reporter Denise Whitaker said, "It is definitely a tragic scene down here. It is a difficult time for all of us this morning."

The helicopter was a Eurocopter AS350, said FAA spokesman Allen Kinetzer.

It was departing from the downtown helipad when it crashed and burned under unknown circumstances, he said. The station said the chopper might have hit the side of a building before it went down.

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